The invention relates to improvements in methods of reducing tension in webs of thermoplastic material, and more particularly to improvements in methods of thermally relaxing such webs.
It is customary to heat thermoplastic webs in order to eliminate the so-called residual shrinkage, i.e., to relax (reduce tension in) such webs preparatory to further processing. As a rule, the web which is to be relaxed is caused to advance through a so-called continuous-flow heater. A drawback of presently known methods is that they cannot ensure predictable and accurate relaxation of thermoplastic webs all the way between as well as in their marginal sections.